;; filter elements
;; get the chars of string
(seq "string")
;; compare char 
(= \h \h) => true
;; class of char
(class \h) => java.lang.Character
;; if it is a character
(char? \h) => true
(number? \h) => false
(char 34) => \"
(char-name-string \newline) => "newline"
(char-escape-string \newline)
[ \space \newline \\ ]
(first "hello") => \h
(ffirst ["hello" "world"]) => \h
(Character/toUpperCase \s) => \S
(vec "hello") => [\h \e \l \l \o]
\newline "\n"
\tab "\t"
\return "\r"
\formfeed "\f"
\backspace "\b"
